DESCRIPTION
The air injection system adds a controlled amount of fresh air to the exhaust gases at the exhaust manifold, or downstream to the catalyst to aid in oxidation of the exhaust gases. This results in reduced levels of carbon monoxide (CO) and hydrocarbon (HC) emissions.
The 5.2L system consists of a belt driven air pump, a switching/relief valve, relief valve solenoid, hoses, and check valves.
AIR PUMP
The air pump is mounted on front of engine and is belt driven. Intake air for the pump is drawn in through a centrifugal filter fan on front of pump. Pump discharge air is directed to air switching/relief valve.
AIR SWITCHING/RELIEF VALVE
This valve directs air injection flow to either a location near exhaust ports or to downstream injection point. The valve also serves as a relief valve at high engine speeds.
A vacuum signal from an Air Switching Relief Valve Solenoid (ASRV-SOL), causes switching valve to open. This routes air pump airflow into exhaust ports. When ASRV-SOL shuts off vacuum to the switching valve, a bleed orifice in the vacuum hose allows vacuum signal to go to zero, causing the switching valve to route pump air to downstream injection point. (Scheme 270)
Scheme 270
CHECK VALVE
This valve is located in the injection tube assemblies that lead to exhaust manifold(s) or to the downstream injection point. Valve has a one-way reed valve which prevents hot exhaust gases from backing up into hoses and pump. This valve protects the system in event of air pump belt failure, abnormally high exhaust system pressure or air hose rupture.
SERVICE PROCEDURES
Complete system should be checked at regular intervals. Engine tune-up should be checked to verify proper engine vacuum whenever air injection system is not operating properly. Belts must be in good condition and set to proper tension.
- Servicing of air pump is limited to replacement of centrifugal fan filter or entire pump. Do not clamp pump in a vise or use a hammer on pump housing. NOTE: DO NOT lubricate air pump. Wipe all oil off of pump housing. Oil in the pump will cause rapid deterioration and failure of internal pump components.
- To replace centrifugal filter, insert needle nose pliers between filter fins and break fan from hub. Install new fan, using pulley and bolts to draw fan down evenly. Do not press or hammer on air pump shaft.
Note. Fan might have a slight squeal until sealing lip is worn in. Air injection system is not completely noiseless. Normal noise increases in pitch as engine speed increases.
AIR SWITCHING VALVE
With engine running, apply vacuum to valve. Air should be injected upstream only. If air escapes from silencer ports or is applied upstream and downstream, valve is faulty and must be replaced.
| CAUTION | Exhaust temperatures are hot. Use extreme care when checking for leaks. |
Remove air supply hose from check valve inlet tube. With engine operating, listen for exhaust leakage at check valve. If exhaust gases escape from valve, valve must be replaced. Also check for leaks at all other connections.